1. FIELD OF THE INVENTION
The present invention relates to a new and improved process for the preparation of dialkyl and diaryl phosphonothioic halides.
2. THE PRIOR ART
Dialkylphosphonothioic halides have been prepared in the past by reacting thionophosphinic acids with PCl.sub.5 according to the following reaction scheme: EQU R.sub.2 P(S)OH + PC1.sub.5 .fwdarw. R.sub.2 P(S)Cl + POCL.sub.3 + HCl. (1)
This reaction is described in Organic Phosphorus Compounds, G. M. Kosolapoff and L. Maier, Vol. 4, p. 158 (Wiley --Interscience, 1972).
A method of preparing dialkarylthiophosphinic chlorides is described in Chemical Abstracts, Vol. 69, p. 10021 at 106875d(1968). According to this method, a mixture of white phosphorus, alkaryl halide and CS.sub.2 or PSCl.sub.3 is heated at 270.degree. to 300.degree. C. in the presence of a catalytic amount of iodine or coiodines. The dialkarylthiophosphinic chloride product is then separated from the mixture.
Dialkyl and diaryl phosphinothioic halides are useful as pesticides and as intermediates in preparation of pesticides and other organophosphorus compounds. The compounds also act as collectors and therefore can be used to increase the effectiveness of flotation of copper ores.